This invention relates to motor control centers having departmentalized cabinets for receiving removable control units which are inserted or withdrawn through open fronts of the respective compartments. More particularly, this invention relates to an interlock between an operator mechanism for switching apparatus of the removable control unit and a unit latch on the removable control unit, the interlock insuring that the latch is in an extended, blocking position when the switch apparatus is in the ON condition to block insertion or removal of the control unit with the switch ON.
Motor control centers comprise a cabinet having a plurality of vertically arranged compartments which open to a forward face of the cabinet. The individual compartments may be of varying height, each defined by a structural transverse wall member extending between the upright walls of the cabinet and separating one compartment from another. Each compartment further comprises a door individual to that compartment hinged on the cabinet at one side of the compartment for closing off the same. Electrically hot bus bars are disposed within the cabinet to commonly extend through each of the compartments. Removable motor control units are insertably received individually within the respective compartments from the open front thereof with the respective door open. The removable control units contain motor control apparatus which may comprise circuit interrupting apparatus such as circuit breakers or fusible disconnect switches each having manual switch operation capabilities. Such circuit interrupting (switching) apparatus has its own operator mechanism, but auxiliary operating mechanisms are provided on the control unit which enable the apparatus to be operated from the exterior of the motor control center cabinet.
For most control units, the switching apparatus is oriented for vertical movement of the operator. However, the smallest size compartment (typically a six inch height) does not permit vertical orientation of the switching apparatus or the operator. These units have the switching apparatus oriented for horizontal operator movement.
The removable control units also comprise plug-in connectors which engage the electrical bus bars within the cabinet when the control unit is fully inserted into the compartment opening. Therefore it is important that the switching apparatus be in the OFF position when either inserting or removing the control unit from the compartment. Accordingly, interlocks are provided on the control unit, usually driven by the operator mechanism, to engage some portion of the cabinet to prevent insertion or withdrawal of the control unit when the switching apparatus is in the ON position.